Combustion equipment and nozzle guide vane assembly with cooling of the nozzle guide vanes



Feb. 5, 1957 A A. GRIFFITH 2,780,060

COMBUSTION EQUIPMENT AND NOZZLE GUIDE YANE ASSEMBLY WITH COOLING OF THE NOZZLE GUIDE VANES Filed Feb. 7, 1952 f 5 Sheets-Sheet 1 llWE/VTOI? A. A. GRIFFITH 2 0 t 6 e 0 e h 0 8 S u 2L e h m s m 5 A E N A V E D m HG mm mm Rm D .N A T N E Feb. 5, 1957 COMBUSTION EQUIPM WITH COOLING OF THE NOZZLE cum:- VANES F'lled Feb 7 1952 M mm w mm W lr 4 My .3 n W Feb. 5, 1957 A. A. RlFFlTH 2,730,060

COMBUSTION EQUIPMENT A NOZZLE cum: VANE ASSEMBLY WITH COOLING OF THE NOZZLE GUIDE VANES Filed Feb. 7, 1952 5 Sheets-Sheet 4 Jfa ' llwmmfl l9. l9- GRIFFITH Feb. 5, 1957 A. A. GRIFFITH 2,780,050

COMBUSTION EQUIPMENT AND NOZZLE GUIDE VANE ASSEMBLY WITH coouuc; OF THE NOZZLE GUIDE VANES 5 Sheets-Sheet 5 Filed Feb. 7, 1952 Ma i/1770f) 14. )4. G'IQ/FF/TH United States Patent COlVIBUSTION EQUIPMENT AND NOZZLE SUEDE VANE ASSEMBLY WETH COOLING OF THE NOZZLE GUIDE VANES Alan Arnold Griflith, Derby, England, assignor to Roiis- Royce Limited, Derby, England, a British company Application February 7, 1952, Serial No. 270,470

Claims priority, application Great Britain February 14, 1%1

3 Claims. (Cl. GIL-39.36) 1 This invention relates to gas turbines of the kind (hereinafter referred to as the kind specified) comprising annular combustion equipment wherein is produced hot gases for driving a turbine. In such a gas turbine the outlet annulus from the combustion equipment coincides substantially with the inlet annulus to the nozzle guide vane assembly of the gas turbine.

Annular combustion equipment normally comprises an outer casing, the downstream end of which is secured to the outer stationary structure of the turbine, an inner casing the downstream end of which is connected to the inner stationary turbine structure, the inner casing being coaxial with the outer casing and located Within it thereby to form an annular fluid passage between the casings, and a flame tube structure within the annular passage comprising a pair of annular walls each of which is coaxial with the casings. Combustion of the fuel being supplied to the combustion equipment is normally ar- 5 ranged to take place in the space between the flame tube walls, and the inner and outer flame tube walls are spaced away from tthe inner and outer casings respectively to leave air passages between the flame tube walls and the inner and outer casings, the air flowing through these passages acting to cool the combustion equipment structure.

Heretofore it has been thought that, since the materials from which say the turbine parts are manufactured have a limited strength at the temperature at which 4 the turbine operates, it is desirable in order to avoid local overheating to maintain a uniform temperature distribution at the outlet from the annular combustion equipment, and for this reason it is usual in annular combustion equipment as above described to allow the air flowing in the air passages to enter the flame tube at points along its length not only to provide combustionsupporting air additional to that entering the flame tube at its inlet end, but also to mix with and cool the hot gases resulting from combustion of fuel, thereby to avoid overheating of the turbine parts.

Heretofore therefore it has been usual to attempt to design annular combustion equipment to obtain a substantially uniform temperature distribution at the outlet from the combustion equipment and at the entry to the nozzle guide vane assembly of the turbine.

I have now found that uniformity of the temperature distribution in the circumferential direction at the outlet from annular combustion equipment is not critical to the uniformity of the temperature assumed by parts 35 of the rotor assembly of a gas-turbine engine and that the rotor assembly, particularly the blades, tend to assume r. a temperature which is a mean of the circumferential temperature distribution, and I employed this discovery to provide an improved construction of annular combustion equipment.

According to the invention in one aspect, a gas-turbine engine comprises annular combustion equipment which includes inner and outer annular casings and inner and outer annular flame tube walls located between and spaced from the casings to afford air passages inside and outside an annular combustion space aflorded between the flame tube walls, and a turbine which is connected to receive hot gas from the combustion equipment and includes at its inlet a nozzle-guide-vane assembly, and a flame tube wall is provided with a part aifording an outlet from the air passage bounded by said flame tube Wall, which outlet-forming part is arranged to deliver a stream of cooling air over the surface of a vane of the nozzle-guide-vane assembly.

According to the present invention in another aspect, a gas-turbine engine comprises annular combustion equipment which includes inner and outer annular casings and inner and outer annular flame tube Walls located between and spaced from tthe casings to afford air passages inside and outside an annular combustion space afforded between the flame tube walls, and a turbine which is connected to receive hot gas from the combustion equipment and includes at its inlet a nozzle-guidevane assembly, wherein a flame tube wall is provided with a plurality of circumferentially-spaced parts each affording an outlet from the air passage bounded by said flame-tubewall, which outlet-forming parts are aligned each with a vane of the nozzle-guide-vane assembly to deliver cooling air over the surface of the associated vane. Preferably both the inner and outer flame tube walls are provided with parts aflording outlets from the air passages bounded by them, there being an outletfo-rming part aligned with each vane of the nozzle-guidevane assembly.

By employing annular combustion equipment of this invention the stationary nozzle guide vanes may be kept cool and thus protected against failure even though the temperature of the combustion gases issuing from the flame tube is in excess of the safe operating temperature for the material from which the vanes are made. As stated above, since the moving blades; of the turbine assume a temperature which is a mean of the temperature at the outlet from the combustion equipment, the rotor blades of the turbine are unaffected by the nonuniform circumferential temperature distribution caused at the outlet from the combustion equipment.

In one preferred arrangement, the outlet-forming parts from the inner of the air passages are arranged to extend across the outlet annulus ina manner substantially to deliver cooling air over the inner halves of the nozzle guide vanes and the outlet-forming parts of the outer wall are arranged to deliver cooling air substantially over the outer halves of the nozzle guide vanes. Thus, with this arrangement each outlet-forming part of the inner wall will be aligned with an outlet-forming part from the outer wall, whereby cooling air is delivered substantially over the whole of the surface of a nozzle guide vane.

In another arrangement according to this preferred feature of the invention, the outlet-forming parts are arranged each to extend across the outlet annulus from the flame tube to substantially the same extent as a nozzle guide vane, and the outlet-forming parts on the inner wall are arranged to alternate with the outletforming parts of the outer wall. With this arrangement cooling air is delivered for alternate vanes from the innermost air passage and for the remaining vanes from the outermost air passage.

According to yet another preferred feature of this invention, the number of vanes in the nozzle guide vane assembly is either equal to or an integral multiple of the number of fuel injectors or burners employed in the 3 annular combustion equipment, and the injectors or burners are arranged so that the hot streaks in the gaseous outflow from the combustion equipment pass between the blades. I

Some embodiments of this invention will now be described by way of example, the description referring to the accompanying drawings in which Figure 1 illustrates diagrammatically a gas-turbine engine having annular combustion equipment according to one embodiment of this invention,

Figure 2 is a view of a segment of the combustion equipment of Figure 1', the view being at the right on the line 2a2a of Figure 1 and being at the left on'the line 2b2b of Figure 1 and being to a larger scale than Figure 1,

Figures 3 and 4 are views corresponding to Figures 1 and 2 of combustion equipment according to a second embodiment, the righ-hand part of Figure 4 being on the line 4a 4a and the left-hand part being on the line 4b-4b of Figure 3, II

Figure 5 is a view corresponding to Figure 1' of a third embodiment of annular combustion equipment,

Figure 6' is a section on the line 66 of Figure 5, and

Figure 7 is a developed view on the line 77 of Figure 5. I I I I Referring to Figures 1 and 2, a gas-turbine engine comprises a compressor 10 having an annular delivery structure, an axial-flow turbine 11 arranged coaxially with the compressor 10 and axially spaced therefrom, and annular combustion equipment 12 connected between the outlet end of the compressor 10 and the inlet side of the turbine 11 and surrounding a shaft 13 connecting the turbine rotor 11a with the compressor rotor (not shown). Fuel is burnt in the combustion equipment to heat air delivered thereto by the compressor, and the heated products of combustion pass through the turbine to drive it. I

The annular combustion equipment 12 comprises an outer air casing member 14 which may be formed in one or more parts, and which interconnects the outlet end of the outer wall 18 of the compressor delivery annulus 10a with the inlet end of an outer shroud 15 for the inlet nozzle guide vanes 16 of the turbine 11. The combustion equipment 12 also comprises an inner air casing 17, which mayalso be formed in any number of parts, located coaxially with and within the outer casing 14 and connecting the inner wall 19 of the compressor delivery annulus 10a with the inner shroud 20 for thenoz'zle guide vanes 16 of the turbine 11. The two casings 14, 17 are thus radially spaced apart so as to afiord an annular duct for working fluid extending between the compressor delivery annulus 10a and the nozz'le-guide-vane assembly 15, 16, 20. I

Arranged within the annular duct is a flame tube into which the fuel to be burnt in the combustion equipment is' delivered by a ring of injectors 21. The flame tube comprises an inner wall 22 and a coaxial outer wall 23, these walls being radially spaced apart from one another, being coaxial with the casings 14, 17 and spaced from the inner and outer casings 14, 17 so as to afford a pair of air passages 24, 25, one outside the flame tube and one inside the flame tube. I II I Air entering the combustion equipment partly enters the flame tube 22, 23 through a mouth afforded between the upstream edges of the walls 22, 23 to provide primary combustion air and partlyflows through the air passages 24, between the flame tube walls 22, 23 and the casings 14,..17. I I, I I As is usual, a number of holes 26 are provided in the flame tube walls 22, 23 to permit secondary combustion air to enter the flame tube to ensure an adequate supply of air to complete combustion of the fuel prior to theworking fluid leaving the combustion equipment. The secondary air holes 26 are in this instance located 4 at points about one-third of the length of the flame tube from its inlet end; I I I The downstream portions of the flame tube walls 22, 23 are shaped to afford outlets 22a, 23a from the passages 24, 25 by which streams of cooling air can be fed over the surfaces of the vanes 16 of the nozzle guide vane assembly 15, 16, 20 of the turbines 11. I

The walls 22, 23 have each a number of flutes 22b, 235 respectively forming these outlets 22a, 23a, which nu'm her (as will best be seen from Figure 2) corresponds to the number of vanes 16 in the nozzle guide vane assembly 15, 16, 20 of the turbine. Each flute 22b, 231) (as will best be seen from Figure 1) increases radially in depth from a point about midway of the length of the corresponding flame tube 22, 23 to the delivery end of the flame tube, and, adjacent the delivery end of the flame tube, each outlet 22a, 23ahas a depth approximately half the extent of a vane 16 of the nozzle guide vane assembly 15, 16, 20. Thus, when the inner and outer walls 22, 23 of the flame tube are assembled, the air flowing in the air passages 25, 24 leaves the passages through the outlets 22a, 23a formed by flutes 22b, 23b, to flow over the surfaces of the vanes 16 forming the nozzle-guide-vane assembly 15, 16, 20, and each vane 16 is cooled substantially over its whole length.

The combustion products leave the flame tube through the spaces 22c, 230 between the outlet-forming flutes 22b, 23b of the flame tube walls 22, 23, which have a spacing substantially corresponding to the spacing of the vanes 16 of the nozzle guide vane assembly 15, 16, 20. The combustion gases flowing between the nozzle guide vanes 16 are substantially uncooled by the air flowing from the air passages 24, 25 downstream of the holes 26 so that the circumferential temperature distribution in the nozzle-guide-vane assembly is not uniform. I

In the second embodiment (Figures 3 and 4), each of the flame tube walls 22, 23 is formed with a number of flutes 22d, 23d forming outlets 222, 23:: equal to half the number of vanes 16 in the nozzle guide vane assembly 15, 16, 20 of the turbine 11, and each outlet 22e, or 23elfrom the air passages 25 or 24 extends axially (Figure 3) from about mid-length of the corresponding flame tube wall 22, 23 to the delivery end thereof and (Figure 4) increases in depth from zero at the mid-length of the corresponding flame tube wall to a radial extent at the delivery end of the flame tube corresponding to the length of a vane 16 of the nozzle-gui-de-vane assembly 15, 16, 20. The inner and outer walls, 22, 23 of the flame tube are arranged so that (Figure 4) the outletforming parts, or flutes, 220! on the inner wall 22 are intercalated with outlet-forming parts 230! of the outer wall 23, and thus air from the air passage 25 is employed to cool each alternate vane 16 of the nozzle-guide-vane assembly 15, 16, 2t) and air from the outermost air passage 24 is employed to cool the remainder of the vanes 16 of the nozzle-guide-vane assembly.

I In the foregoing arrangements the number of burners 'or fuel injectors 21 employed in the combustion equipment 12 is an integral fraction of the number of vanes 16 (and thus the number of vanes 16 is an integral multiple of the number of burners or injectors 21) and the burners or injectors 21 are preferably arranged so that the hot streaks formed in the gas flow by the combustion products tend to pass between the vanes and do not tend to impinge on them, I I

The number of burners or injectors may however be equal to the number of varies in the nozzle-guide-vane assembly and a construction of combustion equipment embodying this and other novel features is shown in Figures 5 to 7.

In this construction, the combustion equipment comprises an outer cylindrical air casing 30 to which is socured internally, as by Welding, curved wall pieces 31', 32 of which wall piece 31 affords the inlet end of the outer boundary of an air passage 33 and of which wall piece 32 affords the outlet end of the outer boundary of the air passage 33. The wall piece 32 has a cylindrical downstream extension 32a which affords the outer shroud of a ring of say 16 nozzle guide vanes 34, the leading edges of which are inclined forwards from their radially inner ends to their radially outer ends.

The combustion equipment also includes an inner air casing 35 which is shaped at its upstream end to form the inlet end of the inner boundary or a second air passage 36 and which carries a curved wall piece 37 to form the outlet end of the inner boundary of passage 36. The inner casing 35 also has secured to it brackets 38 to which is bolted a ring 40 for supporting the downstream edge of wall piece 37, and to which is also bolted an internal flange 39a of an inner shroud 39 for the nozzle guide vanes 34. The inner ends of the vanes 34 are provided with tablets 34a which are Welded to the shroud 39.

The combustion equipment also comprises a flame tube having an outer wall 41 affording the inner boundary of the air passage.33 and an inner wall 42 affording the outer boundary of the inner air passage 36. The upstream edges of the walls are turned over and in the annular gap left between the edges, there are mounted a number of frusto-conical tubes 43, the number being equal to the number of vanes 34 and as will be seen from Figure 6, the tubes 43 are staggered circumferentially with respect to the vanes so as to appear, when the combustion equipment is viewed axially, to be each symmetrically between a pair of vanes 34.

The tubes 43 are connected to the upstream edges of the walls 41, 42 and each supports within it a spider 44, the hub 44a of which is a frusto-conical shroud for a fuel injector 45.

The downstream ends of the walls 41, 42 are formed to provide air outlets from the passages 33, 36 respectively, to deliver cooling air to flow over the nozzle guide vanes 34.

Each wall 41, 42 has a number of slots 46 cut in it from its downstream edge and outlet chutes 47 are fitted in the slots and secured in position on the walls by flanges 47a thereon being welded to the wall. As will be seen from Figure 5, the chutes 47 increase in radial depth in the direction of flow, and the chutes 47 at their downstream ends lie close to the upstream edges of the vanes 34 and have a combined depth equal to the radial extent of the vanes 34.

In this way the vanes 34 are protected against overheating by the products of combustion.

The flame tube is supported at its upstream end by brackets 48 connecting the wall 42 with the inner casing 35 and at its downstream end by dimples 49 formed in the flanges 47a engaging the wall pieces 32 and 37 respectively.

The nozzle-guide-vane cooling arrangements described may also be employed with advantage in multi-stage turbines, it having been found that the non-uniform circumferential temperature distribution created by delivering cooling air from the air passages through the cooling air outlets tends to persist beyond the first-stage rotor blading, so that overheating of the second-stage nozzle-guidevane assembly of a multi-stage turbine may be avoided by suitably selecting its angular position relative to the first-stage nozzle-guide-vane assembly so that the vanes lie in the path of the cooler air delivered over the vanes of the first-stage nozzle-guide-vane assembly.

I claim:

1. A gas-turbine engine comprising annular combustion equipment which includes inner and outer annular casings and inner and outer annular flame tube walls, said flame tube walls being spaced radially to afford an annular combustion space and being radially spaced from the annular casings to afford annular air passages inside and outside said annular combustion space, and a turbine which is connected to receive hot gas from the combustion equipment and which has at its inlet a nozzle-guidevane assembly comprising a plurality of nozzle-guide vanes, each of said flame tube walls terminating at its downstream end close to the upstream edges of the nozzle-guide vanes and being provided with a plurality of flutes which extend from the wall into said combustion space and increase in depth towards the downstream end of the flame tube wall and terminate at said downstream end, there being one such flute aligned with each nozzleguide vane, the flutes on one of the flame tube walls being aligned with alternate nozzle-guide vanes and the flutes on the other flame tube wall being aligned with the remainder of the nozzle-guide vanes, the radial extent of each flute at its downstream end being substantially equal to the radial extent of the associated nozzle-guide vane, whereby a stream of cooling air flows through each flute and is delivered over the surface of an associated one of the nozzle-guide vanes.

2. A gas-turbine engine comprising annular combustion equipment which includes inner and outer annular casings and inner and outer annular flame tube walls, said flame tube walls being spaced radially to afford an annular combustion space and being radially spaced from the inner and outer annular casings to afford annular air passages inside and outside said annular combustion space, and a turbine which is connected to receive hot gas from the combustion equipment and which has at its inlet a nozzle-guide-vane assembly comprising a plurality of nozzle-guide-vanes; one at least of the flame tube walls be ing formed with a plurality of circumferentially-spaced axial slots extending from its downstream end and having a plurality of chute members secured to it with the channel of each chute member in communication with one of said slots, said chute members affording a plurality of air-outlet flutes from the air passage adjacent said flame tube Wall, there being at least one flute aligned with each of the nozzle-guide-vanes, each flute extending to have its downstream end close to the upstream edge of the vane aligned therewith, and the flutes projecting across the combustion space, to extents to provide for each vane air-outlet means over substantially the whole length of the upstream edge of the vane.

3. A gas-turbine engine comprising annular combustion equipment which includes inner and outer annular casings and inner and outer anular flame tube walls, said flame tube walls being spaced radially to afford an annular combustion space and being radially spaced from said annular casings to afford annular air passages inside and outside said annular combustion space, and a turbine which is connected to receive hot gas from the combustion equipment and which has at its inlet a nozzleguide-vane assembly comprising a plurality of nozzleguide vanes, each of said flame tube walls terminating at its downstream end close to the upstream edges of said nozzle guide vanes, each of said flame tube walls being formed with a plurality of circumferentially-spaced axial slots extending from its downstream end and having a plurality of chute members secured to it with the channel of each chute member in communication with one of said slots, said chute members affording a number of flutes equal in number to the number of nozzle-guide vanes and affording air-outlet means from the adjacent air passage, each said flute extending from its flame tube wall into the said combustion space and increasing in depth towards the downstream end of the flame tube wall and terminating at said downstream end, and each flute on one flame tube wall being aligned radially with a flute on the other flame tube wall and being aligned with a nozzle-guide vane, each aligned pair of flutes having at said downstream end a combined radial extent substantially equal to the radial extent of the up-stream edge of the aligned nozzle-guide vane, whereby a stream of cooling air flows through each flute and is delivered over the surface of each of the nozzle-guide vanes.

(References on following page) References Cited .in the file of this .patent UNITED STATES PATENTS Constant et a1. 111137 20, 1948 Price Aug. 7, 1951 Hottel et a1 Aug. 21, 1951 Johnson Mar. 11, 1952 Sedille Apr. 15, 1952 

